St. Sophia's Cathedral is a UNESCO world heritage site consisting of a complex of structures dating from as early as 1037 with numerous additions and renovations made over the centuries reflecting several architectural traditions. It is the most vivid example of Old Rus architecture and monumental art. The cathedral was built and decorated during the reign of Yaroslav the Wise when the state of Kyiv Rus was at the peak of its prosperity. Here grand princes were crowned and buried, formal ceremonies and receptions of envoys were held, the first known library in ancient Rus and the first school for boys and girls were founded. The Cathedral was the seat of the Kyiv Metropolitan. The interior has survived from the 11th century and there have been practically no alterations. Mosaics and frescos of the 11th century, executed with a unique technology that depicts Scriptural scenes, individual figures of Church Fathers, Apostles, warriors and maidens, are of a great cultural and artistic value.